The present invention relates to a method for the wet chemical preparation of materials libraries consisting of a large number of solids, the solids being deposited from reaction mixtures in microreaction chambers onto a bottom plate which simultaneously serves as the library substrate.
The narrowest bottleneck in the development of new active substances, polymers and materials is the discovery of suitable new leading structures. In fields of organic, biochemical and pharmaceutical chemistry, combinatorics has become established within a few years as an important tool for the development of new compounds (e.g., Special issue: Combinatorial Chemistry, Ace. Chem. Res., 1996, 29; G. Lowe, Chemical Society Reviews, 1995, 24 (5), 309;
S. R. Wilson, A. W. Czamik, Combinatorial Chemistryxe2x80x94Synthesis and Application, John Wiley and Sons, 1997). In contrast, only a few examples of using a combinatorial search for materials are known in the field of inorganic solid synthesis and materials research or technical catalyst development. The preparation of materials libraries by combinatorial syntheses has been reported for finding new superconducting materials (X.-D. Xiang et al., Science, 1995, 268, 1738), new magnetoresistant materials (G. Briceno et al., Science, 1995, 270, 273) and new luminescent materials (E. Danielson et al., Science, 1998, 279, 837). A common feature of all these methods is that the application of the substances as thin films by electron beam vaporization or RF sputtering under reduced pressure results in the formation of a materials library. The shape is created by a physical mask, which already resulted in libraries of as much as 25,000 materials. The first combinatorial production of a materials library by a wet chemical method using ink jet technology resulted in the development of luminescent materials (D. Sun et al., Adv. Mater. 9, 1046-1049, 1997). There is a drawback in that this method can only be employed at normal pressure and low temperatures.
Many of the materials known to date, especially the porous substances important to catalysis, can be prepared exclusively by a wet chemical method, often by a hydrothermal process (e.g., M. W. Anderson et al., Angew. Chem., 1995, 107, 1115; D. P. Serrtano et al., Microporous Materials, 4 (1995), 273). These methods are distinguished only by the selected ranges of temperature and pressure, the variation of the stoichiometric proportions of the selected precursors, and the template molecules selected (L. D. Rollmann, Inorganic Compounds with unusual Properties-II, 1979, 387). Depending on the sample volume and experimental procedure, a synthesis under hydrothermal conditions takes from 2 hours to several weeks. This is followed by the further processing and characterization of the product. The most important analytical method is powder diffraction for elucidating the phase structure. Of particular importance to the application of such materials in fields such as catalysis or sensor technology is their pore architecture which can be controlled by the addition of template molecules in hydrothermal synthesis. To date, due to the high expenditure of time for one synthesis and the wide variety of possible mixed oxides and template molecules, a systematic and exhaustive examination of these classes of materials has been impossible. Due to the wide variety of possible polynary mixtures of oxide materials and the generally possible template molecules for influencing the pore architecture of such materials, a transfer of the methods of combinatorial chemistry to hydrothermal synthesis is attractive.
The first application of combinatorial methods in hydrothermal synthesis was reported by Akporiaye, Karlsson and Wendelbo (D. E. Akporiaye, I. M. Dahl, A. Karlsson, R. Wendelbo, Angew. Chem., 1998, 110, No. 5, 629; D. E. Akporiaye, I. M. Dahl, A. Karlsson, P. Wendelbo, patent pending, Norwegian Application No. 97.0788). They developed an autoclave by means of which 100 hydrothermal syntheses (reaction volumes of 500 ml each) at temperatures of up to 200xc2x0 C. can be performed simultaneously. There is a drawback in that this process does not produce a materials library, but the solids produced must be removed from the individual minireactors and individually characterized by standard methods. This kind of handling the samples after synthesis has proven very cumbersome and significantly limits the performance of this combinatorial approach.
In one embodiment of the invention a method for the wet chemical preparation of a materials library comprising a large number of solids from reaction mixtures having different compositions is provided. The reaction mixtures are introduced, in a spatially separated way, into microreaction chambers in removable reaction plates in a reactor and reacted in the form of solutions or suspensions in the microreaction chambers at temperatures of up to 1000xc2x0 C. and internal pressures of up to 1000 bar. The solids produced in the reactions being deposited in a spatially separated way on a removable reactor bottom plate. Preferably, the reactor bottom plate comprises a material that scatters X-rays elastically. Further, reflecting microarea X-ray diffraction may be employed to investigate the materials library deposited onto the reactor bottom plate.